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Feature Article

Diagnosis of Flexible Flatfoot in Children: A Systematic Clinical Approach

Abstract

The goal of this study was to provide measures of symptoms and signs in a consecutive case series of children with flexible flatfoot based on a systematic clinical approach. Fifty-three children (age range, 10-14 years) previously diagnosed with flexible flatfoot were evaluated by a structured interview and clinical assessment. Most patients had foot symptoms (65.3% of feet) and functional limitation (68.3%). Symptoms included a sensation of discomfort (11.3%), such as early tiredness or difficulties during prolonged standing or walking, and pain (54%), mostly located in the plantar aspect of the foot (28.7%) and the medial hindfoot (18.8%). Body mass index was positively correlated to the presence of symptoms and their severity.

Even if an enlarged footprint was present in 93.1% of feet, objective assessment evidenced the presence of heel valgus only in 83% of feet. Forefoot adduction was present in 22% of feet. Jack’s test provided varus correction in only 54% of feet. Internal knee rotation was the most common associated disalignment, present in 43.6% of limbs. Symptoms were significantly correlated to knee alignment, and functional limitation was correlated to heel valgus. Standing balance on 1 leg was significantly correlated to footprint grading severity.

A systematic clinical approach to assess children with flexible flatfoot should always be recommended for the correct diagnosis and the associated treatment management based on symptoms, functional limitation, and foot dysfunction. Functional assessment by specific tests should be included in the examination, as evidence exists that morphology and function are not necessarily related.

Flexible flatfoot is one of the most common musculoskeletal disorders and most debated orthopedic diseases. Harris et al1 divided pediatric flatfoot into symptomatic and asymptomatic, physiological or nonphysiological. While asymptomatic flexible flatfoot is characterized by a natural improvement over time, symptomatic flexible flatfoot alters function and may lead to subjective complaints and objective signs of dysfunction.

Nevertheless, controversy exists about the clinical characterization of flexible flatfoot, the degree of disability it causes in adulthood, and the requirement and choice of treatment.2,3 According to some reports, flexible flatfoot is not a relevant issue as it is asymptomatic and rarely causes disability.4-7 Conversely, others reports that flexible flatfoot may cause gait disorders in adulthood.8-16 Other conditions such as hallux valgus/rigidus, metatarsalgia, subtalar osteoarthritis, tunnel tarsal syndrome, Morton’s neuroma, and posterior tibialis tendon dysfunction are often reported as consequences of a flexible flatfoot deformity. Most forefoot deformities are considered a consequence of abnormal subtalar pronation during propulsion.17

Unfortunately, few longitudinal studies exist on the consequences of flexible flatfoot in adulthood. Furthermore, a consensus on clinical criteria to realize a diagnosis has not been reached. Barry and Scranton18 reported that the diagnosis of flexible flatfoot is an exclusion diagnosis, based on the static morphology and radiographs of the foot. Bordelon19 reported that diagnosis of hypermobile flatfoot should include >1 of the following signs: forefoot abduction, forefoot supination, and heel valgus.

Methods have been suggested to classify the severity of the collapse in the medial arch or to score the broadening of the foot sole.20 Foot morphology and features of the footprint depend on various factors,16-21 and several studies have shown that foot function is not necessarily related to foot morphology.13,22-26

Therefore, flexible flatfoot diagnosis cannot merely rely on a morphologic assessment but should be defined functionally as a foot that, on weight bearing, stays in a state of prevalent or persistent pronation,17 and for which abnormal foot biomechanics could result in fatigue and overuse syndromes over time.18 Thus, the evaluation of flatfoot should include a combination of measures and tests besides morphology that assess the foot’s dynamic status.25

Abstract

The goal of this study was to provide measures of symptoms and signs in a consecutive case series of children with flexible flatfoot based on a systematic clinical approach. Fifty-three children (age range, 10-14 years) previously diagnosed with flexible flatfoot were evaluated by a structured interview and clinical assessment. Most patients had foot symptoms (65.3% of feet) and functional limitation (68.3%). Symptoms included a sensation of discomfort (11.3%), such as early tiredness or difficulties during prolonged standing or walking, and pain (54%), mostly located in the plantar aspect of the foot (28.7%) and the medial hindfoot (18.8%). Body mass index was positively correlated to the presence of symptoms and their severity.

Even if an enlarged footprint was present in 93.1% of feet, objective assessment evidenced the presence of heel valgus only in 83% of feet. Forefoot adduction was present in 22% of feet. Jack’s test provided varus correction in only 54% of feet. Internal knee rotation was the most common associated disalignment, present in 43.6% of limbs. Symptoms were significantly correlated to knee alignment, and functional limitation was correlated to heel valgus. Standing balance on 1 leg was significantly correlated to footprint grading severity.

A systematic clinical approach to assess children with flexible flatfoot should always be recommended for the correct diagnosis and the associated treatment management based on symptoms, functional limitation, and foot dysfunction. Functional assessment by specific tests should be included in the examination, as evidence exists that morphology and function are not necessarily related.

Flexible flatfoot is one of the most common musculoskeletal disorders and most debated orthopedic diseases. Harris et al1 divided pediatric flatfoot into symptomatic and asymptomatic, physiological or nonphysiological. While asymptomatic flexible flatfoot is characterized by a natural improvement over time, symptomatic flexible flatfoot alters function and may lead to subjective complaints and objective signs of dysfunction.

Nevertheless, controversy exists about the clinical characterization of flexible flatfoot, the degree of disability it causes in adulthood, and the requirement and choice of treatment.2,3 According to some reports, flexible flatfoot is not a relevant issue as it is asymptomatic and rarely causes disability.4-7 Conversely, others reports that flexible flatfoot may cause gait disorders in adulthood.8-16 Other conditions such as hallux valgus/rigidus, metatarsalgia, subtalar osteoarthritis, tunnel tarsal syndrome, Morton’s neuroma, and posterior tibialis tendon dysfunction are often reported as consequences of a flexible flatfoot deformity. Most forefoot deformities are considered a consequence of abnormal subtalar pronation during propulsion.17

Unfortunately, few longitudinal studies exist on the consequences of flexible flatfoot in adulthood. Furthermore, a consensus on clinical criteria to realize a diagnosis has not been reached. Barry and Scranton18 reported that the diagnosis of flexible flatfoot is an exclusion diagnosis, based on the static morphology and radiographs of the foot. Bordelon19 reported that diagnosis of hypermobile flatfoot should include >1 of the following signs: forefoot abduction, forefoot supination, and heel valgus.

Methods have been suggested to classify the severity of the collapse in the medial arch or to score the broadening of the foot sole.20 Foot morphology and features of the footprint depend on various factors,16-21 and several studies have shown that foot function is not necessarily related to foot morphology.13,22-26

Therefore, flexible flatfoot diagnosis cannot merely rely on a morphologic assessment but should be defined functionally as a foot that, on weight bearing, stays in a state of prevalent or persistent pronation,17 and for which abnormal foot biomechanics could result in fatigue and overuse syndromes over time.18 Thus, the evaluation of flatfoot should include a combination of measures and tests besides morphology that assess the foot’s dynamic status.25

This article proposes a systematic approach to the diagnosis of flexible flatfoot based on subjective and objective assessments, with the aim of characterizing the main symptoms and signs related to this pathology in a sample of pediatric patients, useful for discriminating nonphysiologic flatfoot.

Materials and Methods

The study group comprised 53 consecutive children (21 girls, 32 boys) aged 10 to 14 years and diagnosed with flexible flatfoot. Mean patient weight was 48.45±14.1 kg, and mean height was 152.4±11.4 cm. Average body mass index (BMI) was 20.5±3.6. Children with congenital and developmental foot diseases, such as tarsal coalition, vertical talus, or cerebral palsy, were excluded. The Institute Scientific Committee approved the study. All patients agreed to participate, and written informed consent was obtained from parents.

Forty-eight children had bilateral flexible flatfoot and 5 had monolateral flexible flatfoot. Data were gathered with respect to the number of feet (with separate data files collected for the right and the left foot for bilateral flexible flatfoot), making a total of 101 feet. A structured interview was conducted consisting of questions about the presence (yes or no) of symptoms in the foot or other sites, such as discomfort, heaviness, tiredness, or pain in the foot during standing or walking; the location of any pain (plantar, medial, or lateral hindfoot; medial or lateral forefoot); and its intensity on a scale of 4 levels: 1=no pain, 2=mild, 3=moderate, and 4=severe (Simple Descriptive Scale27). Functional limitation (yes or no) during activities of daily living, such as standing, walking, and practicing sports, was also investigated.

Clinical measurements of each foot were recorded and consisted of: (a) footprint (taken by print on photographic paper) graded according to Viladot’s score28; (b) heel valgus goniometric measure (alignment between tibia and calcaneus vertical bisection); (c) forefoot adduction/abduction measure (alignment between first metatarsus and rearfoot long axes); (d) hallux valgus measurement (alignment between the hallux first phalanx and the first metatarsal bone long axis)17; (e) range of motion (ROM) for ankle dorsiflexion (with subtalar joint in a neutral position and knee extended); and (f) ROM for ankle inversion/eversion.29

Functional tests were performed to assess the ability to correct the deformity: (a) the great toe extension test (Jack’s test; Figure 1), considered positive when a change in the footprint by 1 grade was evident without considering external tibia rotation25; (b) the tip-toe standing test; (c) and the ability to maintain balance while standing on 1 foot, scored as poor (<5 seconds),="" fair="" (5-10="" seconds)="" and="" normal="" (="">10 seconds).

Figure 1: Example of footprint correction during Jack's test.

Furthermore, lower-limb alignment was characterized by measuring knee deviations with a goniometer while patients stood with feet parallel. Measures were taken in: (a) the coronal plane valgus/varus (using the anterior superior iliac spine, the apex of patella, and the midpoint between malleoli as landmarks); (b) the transverse plane internal-external patella orientation (angle between its anteroposterior axis and sagittal plane); and (c) the sagittal plane flexum/recurvatum (taking the vertical line from the great trochanter to the lateral malleolus with the lateral epicondyle as a fulcrum).

All measurements were taken by the same senior physiatrist (M.G.B.) and are reported in Table 1.

Range of motion, heel valgus and its correction during the tip-toe standing test, hallux valgus, and forefoot adduction/abduction were expressed in terms of mean degrees±standard deviation. Frequency analysis was used for analyzing data such as the presence of symptoms; their location and severity; functional limitation; previous treatments and their duration; presence of knee misalignment; and the presence of heel valgus, hallux valgus, forefoot adduction/abduction, and correction during functional tests.

Pearson’s linear correlation (r value) was used to assess the relationship between age and BMI vs the continuous variables outlined above. The nonparametric correlation Kendall’s tau-b test was performed to study ordinal variables. One-way analysis of variance (ANOVA) was used to test hypotheses of means in different groups. When Levene’s test for homogeneity of variances was significant (P2), calculated by the exact method, was performed to investigate the relationships between sex, stability, pain, and functional limitation vs other clinical parameters.

All analyses were performed using SPSS version 9.0 (SPSS, Inc, Chicago, Illinois).

Results

The structured interview highlighted that most patients had foot symptoms (65.3% of feet) and functional limitation (68.3%) (Figure 2). In 40.6% of feet, they were combined. In 11.9% of feet tested, no symptoms or functional impairment were reported. Among the 65.3% of symptomatic feet, a sensation of discomfort, such as early tiredness or difficulties during prolonged standing, walking, or other motor activities, was present in 11.3% (Figure 2). In the remaining 54% of symptomatic feet, patients experienced pain, which was mostly located in the plantar aspect of the foot (28.7%), followed by the medial hindfoot (18.8%), medial forefoot (12.9%), lateral hindfoot (5%), and lateral forefoot (2%) (Figure 3). In 9% of feet, pain was located in >2 sites. Other sites reported as painful (14.9%) included the ankle (medial or anterior aspect), pretibial zone, and knee.

Figure 2: Subjective reports of pain and other symptoms.

Figure 3: Pain location at the foot and other sites.

With regard to the severity of pain (Figure 4), 34.7% of assessed feet presented with no pain, 52.5% with mild pain, 8.9% with moderate pain, and 4% with severe pain.

Figure 4: Pain grading.

Functional limitation was also assessed during sports activities. Most of the patients (62.4% of feet) reported being able to play sports without difficulty, 28.7% of feet played with difficulty, and 8.9% of feet played no sports. Results for the standing balance on 1 foot test showed that a poor ability was displayed by 33.7% of feet tested, discrete ability by 41.6%, and normal ability by 21.8% (Figure 5).

Figure 5: Distribution of the ability to stand on a single limb.

Heel valgus was present in 83% of feet (with up to 7° considered as normal). Mean heel valgus was 12°±3° (range, 8°-22°).

Hallux valgus was present in 28% feet with a mean of 12.1°±4.8° (range, 7°-20°). Forefoot adduction was present in 22% of feet with a mean of 9.2°±3.5° (range, 4°-15°), and forefoot abduction was present in 4% of feet with a mean of 11°±2.6°.

Mean ankle dorsiflexion was 12.5°±6.8°, while mean plantarflexion was 42.88°±8.6°. Inversion and eversion, measured for the whole foot segment, were 31.1°±10.2° and 16.2°±6.7°, respectively.

An enlarged footprint was present in 93.1% of feet examined and a normal footprint in 6.9%. Of the feet with an enlarged footprint, 12.8% were classified as grade I flatfoot, 12.8% as grade II, 22.8% as grade III, and 44.6% as grade IV (Figure 6).

A total of 54% of feet showed a good ability to correct the heel valgus in varus during tip-toe standing. In the other feet, only a reduction of valgus was measured. The mean alignment during correction was 3°±5° of varus (range, 11° varus-10° valgus).

Measurements of knee alignment in the coronal plane (Figure 7) revealed that in 92.1% of feet no knee malalignment was present, in 5% genu varum was present, and in 3% genu valgus was present. In the sagittal plane, 83.2% of the limbs assessed were normal, recurvatum was present in 14.9%, and flexum was present in 2%. In the transverse plane, 46.6% of limbs had normal alignment, 43.6% had internal knee rotation, and 9.9% had external knee rotation (Figure 8).

Increased age was significantly correlated with a reduced ankle–foot complex dorsiflexion (r=-0.298; P=.003).

Body mass index was correlated with ankle–foot complex range of eversion (r=-0.23; P=.022) and the degree of the footprint during Jack’s test (Kendall’s tau-b=0.02; P=.019). Moreover, BMI was positively correlated to the presence of symptoms and their severity. Specifically, patients with high BMI presented more often with symptoms (ANOVA, P=.03) and with more severe symptoms (ANOVA, P=.001). Standing balance on 1 leg was significantly correlated to BMI such that balance performance decreased with an increase in BMI (ANOVA, P=.05).

Functional limitation was correlated to heel valgus (Mann-Whitney, P=.008). Mean heel valgus of patients referring functional limitation during activities of daily living was 11.3°±4.2°, whereas in the rest of the population it was 9.1°±2.9°.

Discussion

The objective and subjective clinical assessment of flexible flatfoot is an important step in determining an accurate diagnosis. Without an appropriate checklist for diagnosis, the presence of flatfoot and the related clinical aspects can be over- or underestimated. Consequently, unnecessary or inadequate treatment may be undertaken.

According to the Harris et al’s1 algorithm for flatfoot diagnosis, symptoms are fundamental for discriminating physiologic (asymptomatic) or nonphysiologic (asymptomatic or symptomatic) flatfoot. While the former has a natural history of improvement over time, the latter is characterized by progression of dysfunction over time.

Despite the fact that 93.1% of feet diagnosed as flatfoot in our study showed an enlarged footprint, in only 65.3% of feet patients reported symptoms after prolonged stance, walking, or playing sports, and in 54% they reported pain. This finding, albeit higher than in other studies,6 confirms the statement by Harris et al1 about the need to differentiate asymptomatic from symptomatic flatfoot, only the latter requiring treatment. In the present study, pain and functional limitation were often the main reason for seeking treatment. The finding of an enlarged footprint due to flattening of the medial arch is insufficient to allow an accurate diagnosis as previously stated.25 Accurate objective measures and an evaluation of the patient’s subjective complaints must be undertaken to complete the clinical examination.

The most common site of pain in the present study was the foot sole (28.7%), which is generally related to soft tissue tension, such as the plantar calcaneonavicular ligament or plantar fascia. The second most painful site was the medial hindfoot (18.8%), at the distal insertion of the tibialis posterior tendon, highlighting the stress on this muscle that can lead to tendinitis. The presence of symptoms was more frequent in girls than boys, and in patients with increased BMI and knee recurvatum. The latter finding may be responsible for the relative shortening of the triceps surae, frequently associated with severe flexible flatfoot. Knee recurvatum may also be caused by excessive capsuloligamentous laxity, a common physical feature in these patients.1

Functional limitation is another feature of nonphysiologic flatfoot, which in our study was present in a high percentage of cases (67%) and often associated with symptoms (40.6%). It usually consisted of reduced motor performance during activities of daily living, such as walking, running, or jumping. However, 62.4% of the patients said they played sports, although it is important to mention that in most cases the functional limitation confined sports activity to swimming. This finding challenges Tudor et al’s7 statement that flatfoot does not give rise to any disadvantages in sport performance.

Another sign of functional impairment was the ability to maintain balance while standing on 1 foot. It was greatly impaired, since most of the patients (75.3% of feet) were not able to maintain single support for a long time. Since the subtalar joint is responsible for adaptations to instability in the coronal plane, increased eversion of the subtalar joint likely impedes balance during 1-legged standing, because alternating supination at the level of the ankle–foot complex is not possible.16,21 This should be taken into account when assessing function in a child with flexible flatfoot. This is supported also by the correlation found between BMI and standing balance on 1 leg, reduced foot eversion, and poor ability to change the footprint during Jack’s test. Moreover, the correlation found between functional limitations and increased heel valgus can further support this finding.

Reduced ankle dorsiflexion was correlated with age and probably due to Achilles tendon shortening.30 The correlation with age demonstrates that during growth, the Achilles tendon accommodates its length to the heel valgus. A tight Achilles tendon is generally considered both the cause of flatfoot (congenital or asynchronized growing of bone and musculotendon unit)18 and the consequence of heel valgus positioning due to different etiologies (laxity, heel hypoplasia).30 This feature must be carefully evaluated because the need for elongation must be taken into account if surgical treatment is indicated.

Among lower-limb alignment disorders, we found a prevalence of abnormalities in the transverse plane (43.6% knee internal rotation, 9.9% knee external rotation). Although inaccuracy in clinical assessment may occur in this plane, almost half of the patients exhibited internally rotated knees with a convergent patella when measured with their feet parallel.31 This finding is considerable because flatfoot can often represent either a compensation to external tibial torsion as recently reported by Akcali et al32 or a cause of internal rotation of the knee.33 Knee valgus deviation was not common in our study (3%). Inconsistencies with Lin et al’s21 data regarding knock knees as a flexible flatfoot-correlated factor could be explained by the patient’s younger age and the different measuring methods. Lin et al21 used the intermalleolar distance, whereas we measured lower-limb alignment at the knee through anatomical long axes, considering a value of up to 6° of valgus as normal.31 Nevertheless, differences could be simply due to the lower-limb characteristics of the patients examined associated to flexible flatfoot. As reported by Lin et al,21 the opportunity to always evaluate the whole lower limb is recommended in any case because flexible flatfoot may be the consequence of a dynamic functional change of the lower extremity. Since the analysis of correlations between lower-limb alignment and flatfoot was not the main aim of the present study, we focused only on knee alignment as the key joint of the entire lower limb, disregarding hip or tibial torsional deformities, which should be, however, of interest.

Heel valgus was present in 83% of the feet and was more common in boys. Varus correction during tip-toe standing was evident in 54% of feet, whereas in the others there was only a reduction of valgus. The ability to correct the position of the heel in tip-toe standing position is considered a sign of not-fixed flexible flatfoot when the action of the plantar fascia and the medial retromalleolar muscles (flexor longus of hallux, the flexor longus digitorum, and the tibialis posterior) can still reconstruct the medial arch and rotate the calcaneus inward. This functional test combined with Jack’s test represents an important foot functioning test during a simulating gait push-off phase task. According to Root et al,17 a failure in subtalar inversion during the propulsive phase can be responsible for secondary forefoot deformities with time.

Hallux valgus was not a common feature in the examined sample, although flatfoot can be a possible factor leading to its development.15,17 The young age of our patients may explain this finding. Forefoot adduction, considered to be compensation to the abduction imposed by the subtalar joint eversion to stabilize the first ray during propulsion,17 was not common among our patients.

Conclusion

Based on our finding, symptoms and functional limitation are often present in children with flexible flatfoot and must be correctly reported to classify flexible flatfoot. High BMI and female sex are often related to symptoms of flexible flatfoot. Objective clinical measurements, ie, heel valgus and ankle–foot ROM, are necessary to quantify deformities useful for diagnosis and possibly to assess outcomes after treatment. Hallux valgus and forefoot adduction can be measured as well as associated deformities. Functional assessment by specific tests should be included in the examination, as evidence exists that morphology and function are not necessarily related.

A systematic clinical approach to assess children with flexible flatfoot should always be recommended for the correct diagnosis of nonphysiological flexible flatfoot and the associated treatment management based on symptoms, functional limitation, and foot dysfunction.